1. Field of the Invention
The invention relates generally to die casting, and more particularly, the invention relates to interchangeable dies for a die casting machine.
2. Description of the Related Art
An injection molding machine or die casting machine operates at a high speed to produce hundreds of die cast products per hour. Between the production of two different die cast products, the die for forming one part must be removed from the die casting machine and a new die must be inserted into the casting machine to form the new part. Because each die casting machine is a complex mechanical assembly including such parts as lock-out pins, ejector pins, slides, pulls, coolant lines and removable dies or molds to create the desired shapes, it is labor intensive and time consuming to disassemble the machine to change the die. Typically, each die has accessory components such as those previously mentioned that must be detached, reattached and/or appropriately adjusted to accommodate each new die. In addition, a die consists of two or more portions that when closed together define a cavity into which the die cast material, such as zinc, is injected. Each die portion is typically coupled to a shank that serves as a structural frame and connects the die portion to a toggle mechanism of the die casting machine. Because the die portion is secured to the shank, typically by machine screws that extend longitudinally through the shank and engage a rear surface of the die portion, the shank and die portion must be removed together from the die casting machine when changing dies. With current die casting machines and die designs, skilled technicians may spend hours disassembling the machine to remove and reinsert a new die.
As can be appreciated from the foregoing discussion, changing a die in current die casting machines is very time-consuming and may often take as long as several hours. While the dies are changed, the machine recalibrated and the accessories reconnected to conform to a new die, the machine sits idle wasting valuable production time. This idle time is undesirable because it affects the profitability of the machine, e.g. a long downtime to change dies means less parts are produced and thus less profit to the company. So, to maximize the productivity of each die casting machine, the time required to change the die must be reduced. With such a reduction in change time, consumers will benefit because manufacturing costs will decrease and ultimately be passed to the consumer in the form of less expensive products in the stores.
There have been attempts to increase the speed at which dies are changed. In U.S. Pat. No. 5,350,289, a quick change system is disclosed that has a mold base including an ear plate for attachment to the back half of the mold base and an adaptor frame including a pair of U-shaped guide channels for receiving and supporting the ear plate. T-shaped guide rollers are mounted in line with each side of the guide channel to capture the ear plate and keep the ear plate in line with the adaptor frame. While the guide rails and corresponding rollers ease the transferability of the molds, the addition of parts makes the fabrication of the machine assembly more complex and may, therefore, increase manufacturing costs.
In U.S. Pat. No. 5,562,935, an injection molding machine having a multi-port apparatus for connecting multiple coolant lines to a mold during installation is disclosed. While such an apparatus and its corresponding coolant lines may decrease the amount of time required to change the mold base, the multi-port apparatus also increases the complexity of the injection molding machine and may, therefore, complicate die changing and thereby increase manufacturing costs.
Thus, there is a need for an interchangeable die for a die casting machine and a method for changing dies in a die casting machine that reduces the time and labor required to make a die change.
In accordance with a preferred embodiment of the invention, a xe2x80x9cQuick-Changexe2x80x9d die provides an interchangeable die that allows the die or die assembly including the die and its corresponding attachments to be removed from the die casting machine independent of the shank which remains coupled to the casting machine. The interchangeable die construction greatly reduces the amount of time skilled technicians must spend changing dies and overcomes other disadvantages associated with the prior art by eliminating the necessity to disassemble other portions of the die casting machine not directly related to the die itself, such as sensors, coolant lines, mechanical connectors and the like, that are attached to the shank.
In accordance with a further preferred embodiment of the invention, a method, in conjunction with an interchangeable die design, is provided for facilitating the insertion and removal of various dies from a die casting machine.
An interchangeable die system in accordance with the present invention may include two main parts: a shank and a die assembly. The shank is a structural frame that is secured to and remains attached to the die casting machine during a change of the die. The die assembly consists of a die, an adaptor plate and an ejector plate. The die assembly is secured to the shank using the adaptor plate and a locking cam. A spool assembly slides within the shank to actuate the ejector plate assembly. The ejector plate assembly, located within the cavity of the shank, is engaged by the spool assembly.